U.S. Sen. Bernie Sanders of Vermont, the 77-year-old independent who energized youth voters to win Michigan’s Democratic presidential primary in 2016, is coming back to the state this month to campaign for gubernatorial candidate Gretchen Whitmer.

Sanders is set to stump for Whitmer on Oct. 19 in Ann Arbor, her campaign confirmed Tuesday. The venue and start time for the event have not yet been announced.

The democratic socialist is a favorite of the progressive left and endorsed Abdul El-Sayed over Whitmer in Michigan’s Aug. 7 Democratic primary. Whitmer ran to the middle of her primary rivals and was the only candidate in the field who did not echo Sanders’ rallying cry for a single-payer health care system.

The Whitmer campaign is “excited” to have Sanders join her on the campaign trail in Michigan, said spokeswoman Nicole Simmons.

“Sen. Sanders has been on the front lines fighting for hardworking families and we're excited to have him build on the momentum we're seeing in Michigan, drive up volunteer engagement and help turn out voters across the state," Simmons said.

The Schuette campaign criticized the visit as reflecting that Whitmer is out of the mainstream.

"Gretchen Whitmer picked an extreme MoveOn activist as her running mate and now stands with radical Bernie Sanders on a full government takeover of our health care, higher taxes and smaller paychecks for families," campaign strategist John Sellek said. "She is no longer hiding her radical policy agenda that will break our economy and take us backward. We can't afford that."

Sanders will be the latest high-profile surrogate — and potential 2020 presidential candidate — to rally with Whitmer. Democratic U.S. Sen. Kirsten Gillibrand of New York campaigned with the East Lansing Democrat this week in Metro Detroit, and former Vice President Joe Biden campaigned with her in August.

Republican gubernatorial candidate Bill Schuette is endorsed by President Donald Trump and Vice President Mike Pence. who attended a Schuette fundraiser in June. Trump gave Schuette a shout-out during an April visit but has not campaigned here since the primary.

The Associated Press first reported Sanders’ pending visit. It’s one of two kick-off events planned for a multi-state battleground tour he’ll embark on this month in an attempt to benefit Democrats in the mid-term election.

He’s also expected to campaign for candidates in Iowa, South Carolina, Nevada, Wisconsin, Arizona, Colorado and California.

“He wanted to go where he thinks he can be helpful in energizing the base and bringing in young people and independent voters and working-class voters who supported him,” Jeff Weaver, Sanders’ 2016 campaign manager and longtime political adviser, told the AP.

Sanders, who has not yet decided on whether he’ll run for president again in 2020, is a heavy favorite to win re-election the U.S. Senate next month. He is a vocal critic of Trump.